[maybe toxic] spots, how to deal?

So I've got this smallish Japanese natural stone quite a while ago from one of the more reputable vendors. After a couple cleanings and a flattening or two, some bright metallic-looking specks started to appear on the surface.



I didn't know if they would be toxic or not, but they could be felt when running a razor over them so I assumed they were undesirable. Grabbing my diamond plate and trying to flatten them down did not diminish them, and when some were gone, new ones seemed to be revealed.

Took a USB microscope to the specks to see what they look like at moderate magnification:

and also at the highest magnification I could get:

The vendor that sold me the stone did not respond to my questions some months back and I left it alone, but I just picked up this rock again and was thinking it'd be nice to get it sorted out. Anyone have any suggestions? Should I just take a carbide tool and try to dig them out one by one? The stone is pretty hard and for a while I was worried that they were implanted grit from my diamond plate, but I don't really think that's likely.

I don't know if this post will get any attention here, but thought it wouldn't hurt to ask. Thanks!

 

They look pretty at zero magnification. wouldn't any natural stone have impurities in it? If they don't rise above the stone surface, wouldn't they have no effect?

 

There's a chance they are harmless soft metallic inclusions or something...the staining around them seem to be oxidation. I can feel them on the surface barely when I use my fingernail, but I haven't been willing to test a polished razor edge on them to see if they scratch.

 

try a DE or Single edge blade?

 

i see spots like that very often on hard Shoubu and Ozuku
Never had one that was toxic or scratched

 

Cheers, good idea. Running an Astra DE blade over the surface didn't seem to result in lots of deep scratches or chips, but the DE was far from a highly-polished bevel to start with, so I'm not totally confident yet. Still, the specks are large enough that damage from them ought to have been noticeable.

Thanks. I'm a bit relieved now, but I suppose I should still test it some more just to be sure. If the specks aren't harmful, I guess they're nice decoration. Stars Over Shobu Valley.

 

Hurray for $0.18 test blades

 

Trick was holding it on a tongue depressor/popsicle stick to hit the bevel consistently. Bevel on that is pretty rough, which surprised me since I like Astra performance. Thanks again for the tip.

 

I basically know Zero+ about mineralogy, water stones etc., the art of sharpening knives maybe a 2+, but the instant I saw the image, the brain flashed Iron Pyrite.

Later Larry

 

Test it with a Geiger Counter and if all is well, use it.

 

You're using this with a razor and so you should join one of the razor forums and see what they say. Compared to us knife-os, they're really into their stones.

I'm not much of a razor type myself, but - sorry to say - if you can feel those bits when you 'hone' (foreign razor-speak) then I think the razor guys would reject the stone. (And probably say, 'But you can use it on knives.')

Luckily, if you're on this forum and not there then you're more likely a knife user anyway.

 

Was not terribly impressed with the "experts" on the razor fora, so I was just mostly just checking with Maksim here, since emails were either not getting through or getting ignored.

 

I like the idea of using a DE blade rather than a straight to test. Have you tested yet? Curious how this turns out.

 

I have a similar Shuobudani that also has the spots, bought for finishing razors. I asked the same question on srp and mo one was worried as long as your edge isn't being scratched. Feels funny though, as they have a different effect on the draw across the stone.